What’s Photo Stream?
Keep older devices in the picture with this connection to the cloud
Alongside iCloud Photo Library in Photo’s preferences, and in Settings on your iOS devices, is My Photo Stream.
This is an older method of getting photos taken with your iOS devices onto your Mac without using a cable, and it remains useful on older devices that can’t use iCloud Photo Library.
You can think of My Photo Stream as a legacy feature, but it isn’t defunct yet, and won’t be for some time. If you aren’t ready to install at least OS X Yosemite on your Mac, or you have an device that’s stuck on a version of iOS prior to 8.3, it allows you access to your recent snaps, just in a way that’s slightly less convenient than iCloud Photo Library. It can be used as the screen saver on second-generation and later Apple TVs.
The feature differs from iCloud Photo Library in that its contents are ephemeral. Photos uploaded to it persist there for 30 days, and it contains only 1,000 items at a time. To keep a photo on a device, you have to manually save it to an album within that window. Contrast that with iCloud Photo Library being a persistent online copy of all your photos at full quality, available on all of your devices at any time. However, where iCloud Photo Library can use as much online storage as you pay for, My Photo Stream doesn’t count against your quota. It’s also important to note that videos recorded using your iOS devices aren’t uploaded to your stream.
Also, while your Mac will receive full-resolution copies of your photos from your stream, iOS devices and Apple TVs always get a version that’s optimised for their display. So, if you want to keep a photo from the stream at the best quality possible, you’re best off saving it on your Mac.
It’s still partly automatic
New pictures added to your iOS device are automatically uploaded to My Photo Stream when the Camera app isn’t open and the device is online using Wi-Fi, while your Mac can be online over Wi-Fi or Ethernet. It may seem unnecessary to turn on My Photo Stream on a Mac that’s connected to iCloud Photo Library, but it ensures any pics added to your complete library there also go to your photo stream, and then to your older (likely iOS) devices.
Devices need to run at least iOS 8.3 to use iCloud Photo Library. As long as they can run iOS 5.1, they can fall back on My Photo Stream as an alternative.